A man diving for abalone near Point Arena died Thursday morning, the third North Coast casualty related to abalone hunting this year.

No one saw what happened to the 65-year-old Sacramento-area man, and the cause of his death has not been determined, said Mendocino County Sheriff's Deputy Coroner Shannon Barney.

He was reported floating in the ocean near some rocks in Arena Cove just after 10 a.m. Thursday. The cove is southeast of Point Arena.

"We're not sure if it was cardiac-related or a drowning," Barney said.

The death occurred the same day the California Department of Fish and Game enforced abalone-gathering regulations by stopping 294 vehicles and issuing 25 citations at a Highway 1 checkpoint between Fort Ross and Bodega Bay.

The state requires abalone gatherers to immediately tag the mollusks they collect as well as to hold a valid fishing license and abalone report card. Catches are limited to three abalone per day and 24 per year.

The man who died Thursday had dived for abalone and was walking along some rocks with a companion, making his way back to a parking lot, when the two lost sight of each other, Barney said.

The friend found the victim in the water when he came around a bend in the cove, Barney said.

Emergency personnel were unable to revive the man, whose identity was being withheld until his family is notified, Barney said.

The death is another reminder of how treacherous abalone diving can be, he said.

Seven people died last year while hunting for abalone on the North Coast. Some drowned, and others are believed to have suffered cardiac failure.

In early May, abalone hunter Leo Chen, 39, of San Leandro drowned after being swept off the rocks north of Mendocino in rough surf. Several days later, Yasufumi Hamamoto, 58, of Fresno died of cardiac arrest near Sea Ranch while looking for abalone.

You can reach Staff Writer Glenda Anderson at 462-6473 or glenda.anderson@